1. Field of the Invention
The present invention generally relates to a display device, and more particularly to a stereoscopic display device.
2. Description of Prior Art
With the development of liquid crystal display devices, stereoscopic display devices (3D display devices) capable of displaying stereoscopic images have entered the market gradually and become a development direction of the liquid crystal display devices in the next generation.
Please refer to FIG. 1. FIG. 1 illustrates an operational principle of a conventional stereoscopic display device. The conventional stereoscopic display device in FIG. 1 adopts patterned retarder technology, and it displays stereoscopic images in conjunction with polarized glasses 14.
As shown in FIG. 1, a linear polarizer 10 is disposed at one side of a thin film transistor (TFT) array substrate (not shown) of the stereoscopic display device, and a λ/4 wave plate array 12 is disposed at one side of a color filter (CF) substrate (not shown). Light which is generated from a backlight module (not shown) of the stereoscopic display device and passes through the linear polarizer 10 is polarized into linearly polarized light. An angle between an optical axis of the linear polarizer 10 and a horizontal direction H is 90 degrees. Accordingly, only light having a polarizing direction in a vertical direction can pass through the linear polarizer 10. That is, the light passing through the linear polarizer 10 becomes vertical polarized light.
Angles between a direction of an optical axis of the λ/4 wave plate array 12 and the horizontal direction H comprise 45 degrees and 135 degrees. The two directions of the optical axis are alternately arranged along the vertical direction as shown in FIG. 1. Accordingly, after the vertical polarized light from the linear polarizer 10 passes through the λ/4 wave plate array 12, right-hand circularly polarized light and left-hand circularly polarized light are generated at the same time.
The polarized glasses 14 in conjunction with the stereoscopic display device comprise λ/4 wave plates 140 and 142 and vertical polarizers 144 and 146. The λ/4 wave plate 140 is adhered to the vertical polarizer 144 for serving as a left eye glass, and the λ/4 wave plate 142 is adhered to the vertical polarizer 146 for serving as a right eye glass. A direction of an optical axis of the λ/4 wave plate 140 is 45 degrees. A direction of an optical axis of the λ/4 wave plate 142 is 135 degrees. A direction of an optical axis of the vertical polarizer 144 and a direction of an optical axis of the vertical polarizer 146 are perpendicular to the horizontal direction H. The left-hand circularly polarized light from the λ/4 wave plate array 12 can pass through the right eye glass and enter a right eye of an observer, and the left-hand circularly polarized light is absorbed by the left eye glass and does not enter a left eye of the observer. The right-hand circularly polarized light from the λ/4 wave plate array 12 can pass through the left eye glass and enter the left eye of the observer, and the right-hand circularly polarized light is absorbed by the right eye glass and does not enter the right eye of the observer.
Accordingly, when right eye images for the right eye of the observer and left eye images for the left eye of the observer are arranged corresponding to 45 degrees and 135 degrees of the directions of the optical axis of the λ/4 wave plate array 12, the right eye images can be viewed by only the right eye of the observer and the left eye images can be viewed by only the left eye of the observer, thereby 3D effect can be perceived by the observer.
Please refer to FIG. 2. FIG. 2 illustrates a pixel structure of the conventional stereoscopic display device and a patterned retarder film (or called as a film-type patterned retarder, i.e. FPR) 20. A top view is shown in the left of a dotted line, and a side view is shown in the right of the dotted line. FIG. 2 is an in-plane switching (IPS) stereoscopic display device or a fringe field switching (FFS) stereoscopic display device. The patterned retarder film 20 in FIG. 2 functions the same as the λ/4 wave plate array 12 in FIG. 1. That is, when linearly polarized light passes through the patterned retarder film 20, left-hand circularly polarized light and right-hand circularly polarized light are generated. Then, the left-hand circularly polarized light and the right-hand circularly polarized light pass through the polarized glasses 14 in FIG. 1, so that the observer can perceive 3D effect. The pixel structure in FIG. 2 comprises a right pixel region 22 and a left pixel region 24. Each of the right pixel region 22 and the left pixel region 24 is divided into two domains d1 and d2. If each of the right pixel region 22 and the left pixel region 24 has only one domain, color shift phenomenon with a shade of yellow or purple occurs. As a result, an objective of dividing each of the right pixel region 22 and the left pixel region 24 into two domains d1 and d2 is to cancel the color shift phenomenon in a wide angle.
However, the above-mentioned design of the two domains d1 and d2 affects display effect in a vertical viewing angle. The domain d1 is observed from an upward viewing angle 26, and the domain d2 is observed from a downward viewing angle 28. Because liquid crystals in the domain d1 and liquid crystals in the domain d2 have different orientation directions, the problems of the color shift phenomenon and inconsistent brightness between the upward viewing angle 26 and the downward viewing angle 28 occur.
Consequently, there is a need to solve the problems of the color shift phenomenon and the inconsistent brightness due to the above-mentioned design of the two domains in the prior arts.